Re: checkpoints are duplicated even while the system is idle

On Wed, Oct 5, 2011 at 1:19 AM, Fujii Masao <masao.fujii@gmail.com> wrote:
> While the system is idle, we skip duplicate checkpoints for some
> reasons. But when wal_level is set to hot_standby, I found that
> checkpoints are wrongly duplicated even while the system is idle.
> The cause is that XLOG_RUNNING_XACTS WAL record always
> follows CHECKPOINT one when wal_level is set to hot_standby.
> So the subsequent checkpoint wrongly thinks that there is inserted
> record (i.e., XLOG_RUNNING_XACTS record) since the start of the
> last checkpoint, the system is not idle, and this checkpoint cannot
> be skipped. Is this intentional behavior? Or a bug?

If we can eliminate it in some cases where it isn't necessary, that
seems like a good thing, but I'm not sure I have a good handle on when
it is or isn't necessary.

-- 
Robert Haas
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